U.S. Pat. No. 5,875,540, the entire disclosure of which is incorporated by reference herein, discloses a process for forming a stator core in a stator frame. The process involves forming a plurality of core modules or donuts, each of which comprises a plurality of stator core rings laminated together. The stator frame is placed in an upright position. A predefined number of the core modules are then lowered into the upright stator frame. For a power generator which has been in operation for some time and is in need of a new stator core, turning its stator frame upright to receive a new stator core can be very difficult.
U.S. Pat. Nos. 7,302,754; 7,353,586; and 7,395,594, the entire disclosures of which are incorporated by reference herein, are directed at installing stator cores into stator frames without placing the stator frame in an upright position. U.S. Pat. No. 7,202,587, the entire disclosure of which is also incorporated by reference herein, discloses mounting stator core donuts having enlarged grooves in a stator frame using wedges that disperse forces to the donuts in a circumferential manner. The enlarged grooves make installing the donuts less difficult, while the wedges ensure a tight fit of the laminations within the stator frame.
FIG. 1 illustrates a known stator frame 10 for a power generator. The stator frame 10 comprises a main housing 11 for supporting a stator core, not shown in FIG. 1. The main housing 11 comprises an outer structure 13 and a main support structure 15 coupled to the outer structure 13. The main support structure 15 comprising a plurality of stator bore or support rings 18 coupled to the outer structure 13 and a plurality of frame beams 16 coupled to the stator bore rings 18. The main housing 11 further comprises a plurality of dove-tail shaped building bolts or keybars 12 coupled to the frame beams 16. The stator core, not shown in FIG. 1, is supported in the stator frame 10 via the keybars 12.
FIG. 2 illustrates a stator core lamination or donut 14 comprising a plurality of stator core rings (also referred to as laminations) laminated or otherwise coupled together and configured to be supported on the keybars 12 illustrated in FIG. 1. It is noted that a plurality of the stator core donuts 14 are stacked together within the stator frame 10 to form the stator core. Referring now to FIG. 2, each stator core donut 14 includes a plurality of slots or grooves 20 (see FIG. 3) along its outer periphery to receive the keybars 12. The grooves 20 have a dove-tail shape corresponding to the shape of the keybars 12 to ensure a secure and tight fit within the stator frame 10, as more clearly shown in FIG. 3. It is noted that small radial gaps 21 are formed between the periphery of each stator core donut 14 and the inner diameter of the support rings 18, as shown in FIG. 2. It is also noted that one or more mounting assist structures 23A, 23B, 23C may be disposed in each groove 20 between the stator core donut 14 and the corresponding keybar 12. The mounting assist structures 23A, 23B, 23C assist in securing a tight fit between the stator core donut 14 and the keybars 12.